THAT most famous cinematic tornado of all time was a mere illusion. The whirling vortex that swept down the yellow brick road in The Wizard of Oz was not a real tornado, but was created specially for the silver screen by using a fan to blow air through a 60ft high wind sock. And neither was the tornado in the movie
Twister a real time phenomenon; pre-recorded footage was employed, combined with computer generated images and merged with the actions of the actors to produce the desired effects.
Indeed the weather in the movies is seldom the real thing. A director can rarely afford to wait until exactly the right conditions come along and in any event, the real weather tends to be unphotogenic; heavy rain, for example, as many photographers have learned, is very difficult to capture satisfactorily on film. As a consequence, any spectacular weather that we see on screen is almost invariably artificially created and is unrelated to anything that might be happening in the atmosphere.
When Frank Capra, for example, shot It's a Wonderful Life in 1947, the script demanded a snowstorm for the closing scenes. The filming, unfortunately, took place in the middle of a heat wave, but the great director rose to the occasion: the desired effect was achieved by a combination of gypsum - for snow on the ground - and white painted cornflakes for the falling snowflakes.
Rain in any quantity in movies is almost invariably provided by a sprinkler system, with milk, apparently, sometimes added to the mixture to produce a more "visual" type of rain. It is often found too, it seems, that water sprayed upwards produces a more realistic image then sprinklers overhead; thus two protagonists seeming to trudge through a heavy downpour may in reality be merely masked by the effluent from an off camera tanker spraying water skywards.
In the title sequence of the 1952 classic Singing In The Rain, however, where the happy Gene Kelly sings and dances his way around lamp posts and through puddles, wielding that memorably exuberant umbrella, the rain came, as nature intended, from the top. Although it was a nighttime scene, studio economics at the time demanded that it be shot in daylight to avoid the overtime costs that would accrue if it were filmed after dark.
The desired effect was achieved by covering the out door set with tarpaulin, and the rain came from a complex grid of water pipes assembled over the studio "street" to produce a scene that became one of the transcendent moments in American cinematic history.